The present invention relates to a method to provide information in a communications access network that includes a plurality of terminals and a head-end having a plurality of transceivers and further being coupled to each one of the terminals via a downstream common link and a tree-like distributive network. It is also directed to a head-end to provide information and a terminal to receive information realizing such a method, and a communication access network including such a terminal and such a head-end.
Such a communication access network including such a terminal and such a head-end is already known in the art, e.g. from the submission of xe2x80x9cIEEE802.14-95/156, published in Nov. 6, 1995, Protocol Stack and Topology Assumptions for Medium Access Controller (MAC) Level Management Protocol (MLMP) and Medium Access Controller (MAC) Level Access Protocol (MLAP)xe2x80x9d. This submission is provided by the IEEE Project 802.14 Working Group/Standard Protocol for Cable-TV Based Broadband Communication Network. Therein a few topology""s of multiple communication access networks are introduced, more particular on pages 11, 13 and 15.
In order to indicate the background art which can be regarded as useful for understanding the invention, a description is given of the necessary features of the topology of such a communication access network wherein the invention is used.
Such a communication access network includes a head-end and a plurality of terminals. The head-end and each one of the plurality of terminals are communicating with each other by transmitting downstream and upstream information to each other.
In the downstream direction, the head-end is coupled to the plurality of terminals via a downstream common link and a tree-like distributive network. The head-end includes a plurality of transceivers. Each transceiver receives information from the network which is coupled to this communication access network. Such kind of network is e.g. an asynchronous transfer mode network or a synchronous digital hierarchical network and provides information of e.g. a multimedia server or from a router to an internet provider or information from an other access network. It has to be remarked that the kind of network coupled to a communication access network wherein the invention is used and the kind of information provided by the network coupled to the communication access network of the invention are both no restriction to the invention as such. The aim is that each transceiver included in the head-end receives information. The information received by one of the transceivers is modulated to a predefined frequency band and provided by this transceiver in this predefined frequency band to a combiner. The predefined frequency band is associated to this transceiver. In this way the combiner receives a plurality of downstream signals, each one being provided in a different frequency band. The combiner combines all the downstream signals together into one downstream modulated signal. This downstream modulated signal is broadcasted from the head-end to the plurality of terminals.
In the upstream direction each terminal is coupled to one of the plurality of transceivers included in the head-end via an upstream link. This means that each transceiver has its upstream link and that each terminal has access to the head-end via one of these links.
It has to be remarked that a plurality of terminals might have access to one and the same transceiver via one and the same upstream link whereby e.g. in a network terminator a multiple access system e.g. time division multiple access or frequency division multiple access, is used to give access to this upstream link for each one of the plurality of terminals. However, it will be obvious to a person skilled in the art that this feature is not a necessary feature and that this feature gives no restriction on the scope of the invention.
Since a terminal included in a communication access network as described above is only able to transmit information to the transceiver whereto this terminal is upstream coupled, this terminal needs to known which downstream frequency band belongs to its transceiver in order to be able to filter out of the modulated downstream signal a regenerated downstream signal with this downstream frequency band and to have a proper communication with its transceiver. Indeed, without prior knowledge of the configuration of the transceivers i.e. the assignment of the frequency bands to the transceivers, a situation can occur in which a terminal will react on a downstream signal included in the downstream modulated signal coming from another transceiver than the one that is receiving the upstream information of the terminal. Such a situation can cause an interruption or interference of other transmissions being performed by another terminal connected to another transceiver. Such situations should be prevented. By using the preassigned frequency band of its transceiver to filter out of the received modulated downstream signal a regenerated downstream signal which is associated to the downstream signal provided by its transceiver, the terminal is enabled to communicate with its transceiver in a proper way.
An obvious way to give this knowledge to a terminal of an end-user who likes to establish a communication and to have access to the communication access network is to tune the filter of the terminal to the frequency band according to information given to the end-user by e.g. an operator of the communication access network at e.g. installation time of the terminal.
However, a problem outstanding with this method to provide information concerning a filter frequency band is that each terminal has a different installation configuration according to its transceiver whereto the terminal is upstream coupled. In the event when e.g. an end-user moves with his terminal to another place which is located in an environment of an upstream link coupled to another transceiver his terminal has to be reconfigured according to new information to be given by the operator. Moreover, when such a communication access network needs to be reconfigured due to e.g. an increasing number of terminals coupled to the communication access network, new different frequency bands have to be given to the end-users and each terminal needs to be reconfigured on a different new frequency band.
An object of the present invention is to provide a method to provide information concerning a filter frequency band to be used by a terminal e.g. a first terminal, such as the above known method but which has not the above drawback of a different installation configuration for each terminal.
According to the present invention, this object is achieved by a method for use in a communication access network, the communication access network including a plurality of terminals and a head-end which includes a plurality of transceivers, said head-end being downstream coupled to each one of the plurality of terminals via a downstream common link and a tree-like distributive network, each one of the plurality of transceivers providing one of a plurality of downstream signals, in one of a plurality of frequency bands associated to the one of the plurality of transceivers to a combiner included in the head-end, the plurality of downstream signals being together combined into a downstream modulated signal, the downstream modulated signal being broadcasted from the head-end to the plurality of terminals, a first one of the plurality of terminals being upstream coupled to a first one of the plurality of transceivers via an upstream link, the aim of the method being to provide information to the first terminal, the information concerning a filter frequency band being a first one of the plurality of frequency bands and being intended to be used by the first terminal to filter out of the downstream modulated signal a first regenerated downstream signal associated to a first one of the downstream signals provided by the first transceiver, and wherein the method includes the steps of: at predefined time moments distributing by the head-end initialization packets, each one of the initialization packets including a distinct reference and being associated to a respective one of the plurality of transceivers and being included in one of the plurality of downstream signals provided by the one transceiver; the first terminal, upon receiving the downstream modulated signal, filtering out of the downstream modulated signal with one of the plurality of frequency bands a regenerated downstream signal; the first terminal, upon receiving one of the initialization packets included in the regenerated downstream signal, upstream transmitting a confirmation signal which includes the reference of the one initialization packet and an identification of the first terminal; and the head-end, upon receiving the confirmation signal by the first transceiver and in the event that the transceiver associated to the reference does not correspond to the first transceiver, distributing a change request by including the change request in the downstream signal provided by the transceiver associated to the reference, the change request including the identification of the first terminal and the first frequency band associated to the first transceiver (TRX1).
This object is also achieved by a head-end for inclusion in a communication access network and adapted to provide information, the head-end including a plurality of transceivers and being downstream coupled to each one of a plurality of terminals included in the communication access network via a downstream common link and a tree-like distributive network, each one of the plurality of transceivers being adapted to provide one of a plurality of downstream signals in one of a plurality of frequency bands associated to the one of the plurality of transceivers to a combiner included in the head-end, the combiner being adapted to combine the plurality of downstream signals together into a downstream modulated signal which is broadcasted from the head-end to the plurality of terminals, a first one of the plurality of terminals being coupled to a first one of the plurality of transceivers via an upstream link, the information being provided to the first terminal and concerning a filter frequency band being a first one of the plurality of frequency bands and being intended to be used by the first terminal to filter out of the downstream modulated signal a first regenerated downstream signal being associated to a first one of the downstream signals provided by the first transceiver, wherein the head-end further includes: first inserting means to include at predefined time moments initialization packets, each one of the initialization packets including a distinct reference and being associated to a respective one of the plurality of transceivers and is included in one of the plurality of downstream signals provided by the one transceiver, the first inserting means enables thereby the first terminal to receive one of the initialization packets included in a regenerated downstream signal which is filtered out of the downstream modulated signal received by the first terminal with one of the plurality of frequency bands and to transmit an upstream confirmation signal which includes the reference of the one initialization packet and an identification of the first terminal; and second inserting means to include, upon receiving the confirmation signal by the first transceiver and in the event that the transceiver associated to the reference included in the confirmation signal does not correspond to the first transceiver, a change request in the downstream signal provided by the transceiver associated to the reference, the change request including the identification of the terminal and the first frequency band associated to the first transceiver.
This object is still further achieved by a first terminal for inclusion in a communication access network and adapted to receive information and being a one of a plurality of terminals included in a communication access network, the communication access network including a head-end which includes a plurality of transceivers and which is downstream coupled to each one of the plurality of terminals via a downstream common link and a tree-like distributive network, each one of the plurality of transceivers being adapted to provide one of a plurality of downstream signals, in one of a plurality of frequency bands associated to the one of the plurality of transceivers to a combiner included in the head-end, the combiner being adapted to combine together the plurality of downstream signals into a downstream modulated signal which is broadcasted from the head-end to the plurality of terminals, the first terminal being coupled to a first one of the plurality of transceivers via an upstream link, the information being provided by the head-end to the first terminal and concerns a filter frequency band being a first one of the plurality of frequency bands and being intended to be used by the first terminal to filter out of said modulated signal a first regenerated downstream signal which is associated to a first one of the downstream signals provided by the first transceiver, wherein the first terminal further includes: filter means included to receive the downstream modulated signal and to filter out of the downstream modulated signal with one of the plurality of frequency bands a regenerated downstream signal, and to receive an initialization packet included in the regenerated downstream signal, the initialization packet being one of a plurality of initialization packets, each one of the plurality of initialization packets including a distinct reference and being associated to a respective one of the plurality of transceivers and being included in one of the plurality of downstream signals provided by the one transceiver; and confirmation means adapted: to upstream transmit, upon receiving of the initialization packet, a confirmation signal which includes the reference of the one initialization packet and an identification of the first terminal, in order to thereby enable the head-end, upon receiving the confirmation signal by the first transceiver and in the event that the transceiver associated to the reference included in the confirmation signal does not correspond to the first transceiver, to distribute a change request by including the change request in the downstream signal provided by the transceiver associated to the reference, the change request including the identification of the first terminal and the first frequency band associated to the first transceiver.
A further object of the invention is a communication access network that includes such a terminal and head-end(s).
Indeed, the method of the invention includes the following steps
a) the head-end distributes initialization packets, each initialization packet includes a reference and is associated to one of the transceivers and is inserted in the downstream signal which is provided by the associated transceiver.
b) any terminal, e.g. the first terminal which is switched on with the purpose to access the communication access network, filters out of the downstream modulated signal with one of the pre-assigned frequency bands a regenerated downstream signal;
c) the first terminal, upon receiving of such an initialization packet included in the regenerated downstream signal, transmits upstream to its transceiver i.e. the first transceiver, a confirmation signal which includes the reference of the received initialization packet and an identification of the terminal;
d) the head-end, upon receiving of the confirmation signal by the first transceiver of the first terminal and in the event that the first transceiver which is associated to the reference included in the confirmation signal does not correspond to the first transceiver of the first terminal, distributes a change request by including the change request In the downstream signal provided by the transceiver which is associated to the reference, whereby the change request includes the identification of the terminal and the first frequency band which is associated to the first transceiver of the first terminal.
In this way, by using the method of the invention to log on a terminal to the access system, no different installation configuration is needed for different terminals and no prior knowledge is needed for the end-user. Indeed, when using the method of the invention and when a terminal receives a change request of the head-end, the terminal is tuned to the provided filter frequency band which is a correct frequency band to establish a communication between the terminal and its transceiver.
A remark is that step a) and step b) of the invention implicates that the initialization packets are included in the downstream signals and that a terminal, at access time, listens to a frequency band which is e.g. predefined during production or which is chosen at random at the time the terminal is switched on. A possible implementation of these two steps a) and b) is to define a downstream booting frequency band associated to a predefined downstream booting signal provided by a booting transceiver and used for inclusion of at least a plurality of the initialization packets. The downstream booting signal is used by all terminals willing to get access to the communication access network.
A first advantage of such a downstream booting frequency band is that all terminals during production can be performed following one and the same production process which provides a terminal which at access time starts filtering with a frequency band associated to this one predefined downstream signal i.e. the downstream booting channel.
A second advantage of this way of implementation becomes clear with a situation wherein all initialization packets are included in the downstream booting signal and all terminals are listening at start up to the booting frequency band according to this downstream booting signal. In this case, no association of an initialization packet to a transceiver in order to known to which downstream signal a terminal is listening has to be remembered. No memory means have to be implemented in the head-end for this purpose. Indeed, the head-end only has to known which transceiver received a confirmation signal and distributes a change request, included in the downstream booting channel, with the information of the identification of the terminal and the frequency band associated to the transceiver which received the confirmation signal of the terminal.
In addition, an additional implementation is given in order to realize step c) and step d) of the method of the invention. Indeed, the transmission of the upstream confirmation signal can be realized in a predefined upstream frequency band which is also used by each transceiver to receive the confirmation signal.
A further way of implementation with the object to realize the method of the invention as simple as possible is to define the time moment of sending an initialization packet as the reference of that initialization packet.
It has to be explained that two kinds of multiple access are known in the art: a fixed assignment multiple access system whereby a terminal has periodic access to a head-end or a demand-assignment multiple access system whereby a terminal requests access to a head-end by e.g. reacting on a ranging grant which have been sent by his head-end. For both multiple access types some initialization steps have to be executed e.g. distance equalization, power leveling.
In the event of a demand-assignment multiple access system, before performing such above initialization steps, a ranging process has to be performed in order to provide to the head-end the knowledge of the identification of a terminal willing to log on to the access system. As described above, a terminal willing to log on reacts on a ranging grant which is in fact a permission of the head-end for the terminal to sent information.
Such a ranging grant, a reaction packet of a terminal on such a ranging grant and initialization packets exchanged between a head-end and a terminal to realize such above mentioned initialization steps are called hereafter multiple access initialization packets.
This brings us to another characteristic feature of the present invention whereby the initialization packets or the confirmation signal or the change request are integrated in multiple access initialization packets. An advantage of implementing the method of the invention in this way will be explained with the following example. Indeed, by including e.g. an initialization packet of the invention in a ranging grant, the reaction of a terminal to this ranging grant includes anyway the identification of the terminal whereby a number of bits to be transmitted can be saved by including the confirmation signal of the invention in the reaction of the terminal to the ranging grant.
It has to be remarked that once a terminal knows its filter frequency and once a communication between a terminal and its transceiver is established, a downstream and upstream data frequency band can be communicated between each other in order to be used during the transmission of data information.
It has to be explained that associating an initialization packet to a transceiver is giving the possibility to one terminal which is upstream coupled to this transceiver to get access to the access system. In order to give to the terminals coupled to the access communication network a substantial equally chance to get access to the access system, the association of the initialization packets to the transceivers are spread over the plurality of transceivers following a relation which is directly proportional to the number of terminals which are coupled to each one of the plurality of transceivers.
Furthermore, it has to be remarked that in the event that the transceiver associated to the reference included in the confirmation signal corresponds to the transceiver whereto the terminal is coupled, it is not necessary to transmit a change request since the frequency band used by the terminal is already the good one. Indeed a possible implementation of the method of the invention is to confirm in such a situation that the filter frequency band to be used is the frequency band which was already used by the terminal to filter out of the downstream modulated signal a regenerated downstream signal to receive an initialization packet. It has to be remarked that a possible implementation of this feature can be realized by e.g. sending a filter frequency band confirmation signal from the head-end to the terminal or providing at the terminal the knowledge that after passing a predetermined time from executing step c) of the invention without receiving step d) of the invention, the actual used frequency band is assumed to be the good one.
It is further to be noticed that the term xe2x80x9cincludingxe2x80x9d, used in the claims, should not be interpreted as being limitative to the means listed thereafter. Thus, the scope of the expression xe2x80x9ca device including means A and means Bxe2x80x9d should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the devices are A and B.
Similarly, it is to be noticed that the term xe2x80x9ccoupledxe2x80x9d, also used in the claims, should not be interpreted as being limitative to direct connection only. Thus, the scope of the expression xe2x80x9ca device A coupled to a device Bxe2x80x9d should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means.
It has to be remarked that the information concerning a filter frequency band can be stored in a memory of a terminal after being provided to this terminal. The following time that the terminal is switched on, it is possible to check first the availability of a good filter frequency band in the memory of the terminal. In the event that such a good filter frequency band is available it is not necessary to execute the method of the invention but the available good filter frequency band can be used immediately to filter out of the modulated signal a regenerated downstream signal associated to a downstream signal and provided by the transceiver of the terminal. Only in the event that a reconfiguration of the access network took place between the time that the filter frequency band was memorized by the terminal and the time that this filter frequency band is re-used by the terminal as a good filter frequency band the steps of the method of the invention will have to be executed.